Flash memory is nonvolatile computer storage that can be electrically erased and reprogrammed. In general, flash memory has a high resistance to mechanical shock, small foot print, relatively fast read times that are comparable to dynamic Random Access Memory (RAM), is energy efficient and can store data for years without power. Flash memory is used in a variety of applications, including personal computers, mobile devices, digital cameras, video games, scientific instrumentation, industrial robots, medical electronics and other devices.
Flash memory has several limitations, including slow write times and limited lifetime. For flash memory, the write times are typically an order of magnitude greater than the read times. The lifetime of various types of flash memory typically ranges from 1000 to 100,000 erase cycles. The erasure of the flash memory causes incremental damage that eventually leads to failure of the memory mechanism in the flash memory.
Flash memory is used in conjunction with a wide variety of technologies, including Universal Serial Bus (USB) devices. For example, a solid state memory device can be created with a bank of flash memory that accessed using a USB controller and USB protocols. The USB specification is an industry standard developed that defines cables, connections, and communication protocols used to communicate and supply power between computers and electronic devices. The USB standard continues to evolve to faster data transfer speeds and greater power transfer capability. USB 2.0 has a maximum bandwidth of 480 Megabits/second (60 Megabytes/second) and power transfers of 1.5 amperes. USB 3.0 has 5 Gigabits/second (625 Megabytes/second) and power transfers of 1.5 amperes, with a maximum current of 5 amperes. There are billions of USB interfaces and USB enabled devices in the global market place with about 2 billion additional USB enabled devices being sold each year. One application for USB technology is in data storage devices. USB data storage devices typically include flash memory with an integrated USB interface, are relatively small, and removable/rewritable. While USB devices support USB connectivity, even the fastest USB drives do not currently support the full transfer rate of the USB specification and fall considerably short of the transfer rate possible from a current generation hard disk.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.